热处理条件下激光原位合成高铌Ti-Al金属间化合物复合涂层的微结构特征  

Microstructure characteristics of laser in situ synthesis high Niobium Ti-Al intermetallic compound coating under heat treatment

作　　者：刘洪喜[1] 李正学[1] 张晓伟[1] 郭新政 王悦怡[1] 

机构地区：[1]昆明理工大学材料科学与工程学院,云南昆明650093

出　　处：《光学精密工程》2017年第6期1477-1485,共9页Optics and Precision Engineering

基　　金：国家自然科学基金资助项目(No.61368003;No.11674134);云南省应用基础研究计划重点项目(No.2016FA020);云南省中青年学术技术带头人后备人才资助项目(No.2014HB007)

摘　　要：为了提高钛合金的高温抗氧化性能,推动钛合金在高温和复杂工况环境下的进一步工程应用,利用高能激光束作用下Ti、Al、Nb三种元素混合粉末之间的原位反应在BT3-1钛合金表面制备了高温抗氧化的高铌Ti-Al金属间化合物复合涂层。针对原位反应所制备涂层存在的缺陷,通过自行设计的热处理工艺优化了涂层和界面微观组织。借助光学显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)分析了热处理前后复合涂层的物相结构及显微形貌。结果表明:热处理前的涂层主要由单质Nb、金属间化合物γ-TiAl、α_2-Ti_3Al、Ti_3Al_2等物相组成;热处理后的复合涂层,单质Nb固溶到γ-TiAl和α_2-Ti_3Al中,同时形成了新相Ti_3AlNb_(0.3),涂层近似为γ-TiAl+α_2-Ti_3Al双相层片状等轴晶组织。此外,涂层中并未观察到减弱抗氧化性的单质Nb颗粒和Ti_3Al_2相,Ti、Al、Nb的宏观偏析得以消除,涂层与基材界面位置的气孔和裂纹均以消失,出现了明显的白亮带冶金结合过渡层,涂层组织也更加均匀致密。热处理对提高钛合金表面Nb的合金化程度和改善Ti-Al金属间化合物的高温抗氧化性能起到了显著的促进作用。In order to improve the high-temperature oxidation resistance and further promote the engineering application of titanium alloy in high temperature and complex service environment conditions,high niobium Ti-Al intermetallic compound oxidation resistance coatings were prepared on BT3-1titanium alloy surface by laser in situ synthesis process.Microstructure of the composite coating and interface was optimized through a self-designed heat treatment process according to the defects in the coating.The phase structure and microstructure of the coating before and after heat treatment were analyzed by Optical Microscope（OM）,X-Ray Diffraction（XRD）and Scanning Electron Microscopy（SEM）.The results show that the coating mainly consists of Nb,intermetallicγ-TiAl,α_2-Ti_3Al and Ti_3Al_2 phases before heat treatment.But after heat treatment,the Nb is dissolved inγ-TiAl and α_2-Ti_3Al,and new phase Ti_3AlNb_（0.3） is observed in the coating.The microstructure of the coating is approximatelyγ-TiAl＋α_2-Ti_3Al biphasic lamellar equiaxed grains structure.Moreover,the element Nb particle and Ti_3Al_2 phase which weaken inoxidizability are not observed in the coating.The macro segregation of Ti,Al and Nb is eliminated,and the pores or cracks at interface positions between the composite coating and substrate are disappeared.A distinct white band transition metallurgical bonding layer is generated,and the microstructure of the coating is more uniform and dense.Heat treatment plays an important role in improving the Nb alloying extent on titanium alloy surface and increasing the high temperature oxidation resistance of the Ti-Al intermetallic composite coating.

关 键 词：激光原位合成 热处理 Ti-Al金属间化合物 复合涂层 微观组织 

分 类 号：TN249[电子电信—物理电子学] TB331[一般工业技术—材料科学与工程]